• Refractive Mgmt/Intervention

    In this study, the authors describe a novel technique for the treatment of keratoconus using femtosecond-assisted corneal allogenic intrastromal ring segments (CAIRS).

    Study design

    Allogenic rings were prepared from donor corneas using a specially designed double-bladed circular trephine, as seen in this video.

    Investigators enrolled 20 patients (24 eyes) with progressive keratoconus who received the implant followed by accelerated epi-off corneal crosslinking (CXL). The host channels were created at 50% depth using a femtosecond laser with a 6.5-mm inner and an 8-mm outer diameter. Accelerated CXL was accomplished using 10 mW/cm2 for 9 minutes for a total energy of 5.4 J/cm2. A bandage contact lens was used if the thinnest pachymetry was less than 400 microns.


    During follow-up (range 6 – 18 months), investigators found significant gains in uncorrected and corrected distance visual acuity (up to 8 lines and 5 lines, respectively). No eye showed progression during the entire follow-up.

    Spherical equivalent, simulated maximum keratometry, steepest keratometry, topographic astigmatism, anterior and posterior best sphere, and mean power in the 3- and 5-mm zones were also significantly improved from baseline.

    All segments remained well positioned with no intra- or postoperative complications.


    A long-term follow-up is needed to fully determine the safety profile of this technique. It would have been interesting to see the keratometry-flattening effect of the allogenic implant alone without the addition of CXL.

    Clinical significance

    These are promising preliminary findings from this novel technique. Replacing currently available intracorneal ring segments with allogenic tissue could significantly reduce long term complications such as scarring, haze, extrusion or displacement. The technique may also be a cost-efficient method for improving refraction in patients with keratoconus.